Field of the Disclosure
Embodiments of the disclosure relate to a touch sensing system and a method for driving the same capable of sensing a pen and a finger.
Discussion of the Related Art
A user interface (UI) is configured so that users are able to communicate with various electronic devices and thus can easily and comfortably control the electronic devices. Examples of the user interface include a keypad, a keyboard, a mouse, an on-screen display (OSD), and a remote controller having an infrared communication function or a radio frequency (RF) communication function. User interface technology has continuously expanded to increase user's sensibility and handling convenience. The user interface has been recently developed to include touch UI, voice recognition UI, 3D UI, etc.
The touch UI has been indispensably used in portable information appliances and has been expanded to the use of home appliances. The touch UI senses a location of a finger or a pen touching a touch screen and generates location information.
The touch screen is classified into a touch screen sensing a conductor, for example, the finger, and a touch screen sensing the pen. An example of the latter pen touch screen is disclosed in U.S. Pat. No. 7,903,085 (Mar. 8, 2011) (hereinafter, referred to as “a related art pen touch sensing device”). The related art pen touch sensing device includes a special pen including a resonant circuit embedded therein, a loop antenna receiving a resonance signal from the special pen, and an analog signal processing unit extracting location information and pen pressure information of the special pen from a signal of the loop antenna.
As shown in FIG. 1, in the related art pen touch sensing device, a square wave signal for inducing a resonance of a pen PEN is propagated through an electromagnetic resonance path through an antenna ANT and is transmitted to the pen PEN. A resonance signal generated from a resonant circuit of the pen PEN is propagated through the electromagnetic resonance path, i.e., an electromagnetic field, and is received by the antenna ANT. The resonant circuit of the pen PEN is resonated by the square wave signal received through the electromagnetic field and transmits the resonance signal to the loop antenna in the electromagnetic field. Thus, in the related art pen touch sensing device, the pen PEN and the antenna ANT transmit and receive the resonance signal in the electromagnetic field.
The related art pen touch sensing device, however has the following disadvantages.
The related art pen touch sensing device requires the plurality of loop antennas and switch circuits for sequentially driving the loop antennas, so as to detect a touch location of the pen in an XY coordinate system. The loop antennas have to be implemented in an overlapped shape in a matrix form, so as to recognize a touch point in the XY coordinate system. Further, because a separate antenna layer has to be added to a display panel so as to implement the loop antennas in the display panel, the thickness of the display panel increases. Because a structure for connecting the plurality of loop antennas and the analog signal processing unit to the display panel has to be added, a cable connection equipment becomes large and complicated. Thus, when the plurality of loop antennas are integrated in the display panel, it is difficult to provide a slim and simple display device.
Because the related art pen touch sensing device compares received signals of the pen using an analog comparator, only the presence or absence of the pen may be recognized and it is difficult to accurately represent coordinates of the touch location of the pen. Because a pulse generator used in the related art pen touch sensing device limits a frequency of the resonance signal, it is difficult to change a resonant frequency. Because the analog signal processing unit used in the related art pen touch sensing device shows different operation results depending on a surrounding environment, such as a temperature and humidity, its reliability is low.